Thermocouple holder for furnance tube

ABSTRACT

A thermocouple holder assembly for a furnace tube including a heat sink block for welding to the furnace tube, the heat sink block having a first bore therein for slidably receiving the distal end of an elongated sheathed thermocouple, the heat sink block having a hollow heat sink tube extending from the first bore for receiving a portion of the thermocouple, and a heat shield for welding to the furnace tube having walls for shielding and completely enclosing the heat sink block to shield the heat sink block from ambient heat on the exterior of the heat shield, the heat shield having a cavity therein for receipt of the heat sink block and the heat sink tube and flexible insulation material placed over the heat sink block and the heat sink tube, one of the walls having a second bore extending therethrough to the cavity for slidably receiving the thermocouple, the second bore being positioned in-the heat shield wall for alignment with the heat sink tube for conveying the thermocouple through the second bore to the heat sink tube, the heat shield having a third bore extending through one of the walls and intersecting the second bore for receipt of a fastener for placement in the third bore for selectively fastening the thermocouple to the heat shield and for selectively releasing the thermocouple from the heat shield.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to furnaces or heaters, and moreparticularly to apparatus for measuring the temperature in furnaces orheaters. Even more particularly, the present invention is related tothermocouples used to measure the temperature of furnace or heatertubes, and apparatus for attaching thermocouples to furnace or heatertubes.

[0003] 2. Description of the Prior Art

[0004] Thermocouples are commonly attached to furnace or heater tubesused in industrial applications to monitor the temperature of thesurface of the tube to prevent damage to the tube from excessivetemperatures. Such heaters or furnaces are well known in the art and areused to heat fluids flowing through the tubes.

[0005] Apparatus for attaching such thermocouples to the surface offurnace or heater tubes are known in the art. Exemplary of the relatedart are the following U.S. Pat. Nos.: 2,048,680; 2,048,681; 2,151,648;3,143,439; 3,901,080; 3,939,554; 4,854,729; 4,971,452; 5,172,979;5,382,093; 5,993,061; and 6,334,707.

[0006] It is also known in the art to connect thermocouples directly toheated bodies such as furnace or heater tubes by welding, or peening orswaging into a hole drilled in the heated body or fastener such as aclip connected to the heated body. Shields and insulation are thenplaced over the thermocouple to prevent damage to the thermocouple andare welded to the heated body.

[0007] Commonly, removal and replacement of thermocouples requireswelding a new thermocouple directly to a furnace tube or to an apparatusconnected to a furnace tube. Damage may be done to the tube duringremoval of the old thermocouple and the welding of the new thermocoupleto the furnace tube, and the tube may require removal from the furnaceand re-welding to the furnace after the thermocouple is replaced.

BRIEF SUMMARY OF THE INVENTION

[0008] In accordance with the present invention there is provided athermocouple holder assembly for a furnace tube including a heat sinkblock for welding to the furnace tube, the heat sink block having afirst bore therein for slidably receiving the distal end of an elongatedsheathed thermocouple, the heat sink block having a hollow heat sinktube extending from the first bore for receiving a portion of thethermocouple, and a heat shield for welding to the furnace tube havingwalls for shielding and completely enclosing the heat sink block toshield the heat sink block from ambient heat on the exterior of the heatshield, the heat shield having a cavity therein for receipt of the heatsink block and the heat sink tube and flexible insulation materialplaced over the heat sink block and the heat sink tube, one of the wallshaving a second bore extending therethrough to the cavity for slidablyreceiving the thermocouple, the second bore being positioned in the heatshield wall for alignment with the heat sink tube for conveying thethermocouple through the second bore to the heat sink tube, the heatshield having a third bore extending through one of the walls andintersecting the second bore for receipt of a fastener for placement inthe third bore for selectively fastening the thermocouple to the heatshield and for selectively releasing the thermocouple from the heatshield.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0009]FIG. 1 is a perspective view, partly cut-away, of the heat sinkblock of the thermocouple holder assembly of the invention;

[0010]FIG. 2 is a cross-sectional view of the thermocouple holderassembly of the invention taken along lines 2-2 of FIG. 1;

[0011]FIG. 3 is a cross-sectional view of the thermocouple holderassembly of the invention taken along lines 3-3 of FIG. 1;

[0012]FIG. 4 is a perspective view of the heat shield of thethermocouple holder assembly of Figure of the invention showing a hollowcavity therein in phantom lines;

[0013]FIG. 5 is a cross-sectional view of the heat shield of thethermocouple holder assembly of the invention taken along lines 5-5 ofFIG. 4;

[0014]FIG. 6 is a cross-sectional view of the heat shield of thethermocouple holder assembly of the invention taken along lines 6-6 ofFIG. 1;

[0015]FIG. 7 is a perspective view, partly cut-away, of the thermocouplepin of the thermocouple holder assembly of the invention;

[0016]FIG. 8 is an exploded, perspective view, partly cut-away, of thethermocouple holder assembly of the invention and a thermocouple alignedfor connection to a furnace tube;

[0017]FIG. 9 is a perspective view, partly cut-away, of the thermocouplepin of the thermocouple holder assembly of the invention connected to afurnace tube with a thermocouple therein and the thermocouple pinremoved therefrom to enable removal of the thermocouple therefrom in thedirection indicated by the arrow; and

[0018]FIG. 10 is a perspective view, partly cut-away, of thethermocouple pin of the thermocouple holder assembly of the inventionconnected to a furnace tube with a thermocouple aligned for insertiontherein in the direction indicated by the arrow adjacent thereto and thethermocouple pin aligned for insertion in the heat shield in thedirection indicated by the arrow after insertion of the thermocoupletherein.

DETAILED DESCRIPTION OF THE INVENTION

[0019] Referring now to the drawings, in FIGS. 8-10 is shown thethermocouple holder assembly of the invention generally indicated by thenumeral 20. Thermocouple holder assembly 20 includes a heat sink blockassembly generally indicated by the numeral 22 shown in detail in FIGS.1-3, and in FIGS. 8-10 connected to furnace or heater tube 23, and aheat shield generally indicated by the numeral 24. The word “furnace”used herein has the same meaning as the word “heater”.

[0020] Heat sink block assembly 22 includes a solid metallic integrallyformed heat sink block generally indicated by the numeral 22 a having aflat bottom face 26 which is generally rectangular in shape. If desiredbottom face 26 could be slightly concave to fit the curvature of furnacetube 23. Top face 28 is generally rectangular in shape and is locatedabove bottom face 26 parallel thereto. Preferably, top face 28 is thesame length as bottom face 26 and is wider than bottom face 26.

[0021] Two generally rectangular sloping side faces 30 and 32 connecttop face 28 to bottom face 26. Two trapezoidal end faces 34 and 36 arelocated at each end of heat sink block 22 a. If desired, end faces 34and 36 could be rectangular or any other desired shape which wouldpermit a heat seal with furnace tube 23 sufficient to enable the heatsink block 22 a to reach substantially the same temperature as furnacetube 23.

[0022] As shown in FIG. 2, end face 34 has a generally horizontalcentral cylindrical bore 34 a therein which extends into the interior ofheat sink block 22 a generally parallel to bottom face 26, top face 28,and side faces 34 and 36. Hollow heat sink tube 38 is snugly received inbore 34 a and is preferably force-fitted therein. Preferably heat sinktube 38 is a metallic material.

[0023] Horizontal bore 34 a extends from end face 34 to vertical bore40. Vertical bore 40 extends from the bottom face 26 of heat sink block22 a to the top face 28. Vertical bore 40 may be omitted if desired, butis preferred to enable small amounts of air inside heat sink tube 38 tobe vented upward through vertical bore 40 when thermocouple 42 is forcedinto the interior 38 a of heat sink tube 38. Bore 34 a continues to endbore 34 b located on the other side of vertical bore 40 a slightdistance to receive the distal end of thermocouple 42 when the distalend of thermocouple 42 is inserted in heat sink tube 38 and onward intobore 34 a and end bore 34 b. Thermocouple 42 may be any common sheathedthermocouple well known in the art.

[0024] Heat sink block 22 a is connected to the surface of furnace tube23 by welding along the lower edges of sides 30 and 32. Welding beads 44shown in FIGS. 8 and 9 are welded along the lower edges of sides 30 and32 of heat sink block 22 a to bond heat sink block 22 a securely to theouter surface of furnace tube 23. Preferably, two passes of weldingbeads 44 are made along the entire length of both lower edges of sides30 and 32 to insure proper heat transfer from the surface of the furnacetube 23 to heat sink block 22 a.

[0025] As shown in FIG. 8, covering heat sink block 22 a and heat sinktube 38 is solid metallic integrally formed heat shield generallyindicated by the numeral 20. Heat shield 20 is generally rectangular inshape, having a top rectangular face 46 and a parallel partial bottomface 48 having the lower opening to cavity 50 therein for receipt ofheat sink block 22 a. Two rectangular parallel side faces 52 and 54extend downward perpendicular to top face 46 to bottom face 48, and tworectangular end faces 56 and 58 are located at each end of heat shield24.

[0026] As shown in FIGS. 5-10, end face 56 has a generally horizontalcylindrical bore 56 a therein which extends into cavity 50 of heatshield 24 generally parallel to bottom face 48, top face 46, and sidefaces 52 and 54. Cylindrical bore 56 a receives thermocouple 42.

[0027] Intersecting perpendicularly and horizontally with heat shieldbore 56 a is horizontal cylindrical fastener bore 60. Cylindricalfastener bore 60 preferably extends completely through heat shield 24from face 52 to face 54 to receive preferred thermocouple locking pin62. However, if a bolt, screw, or other fastener were used to lockthermocouple 42 in bore 56 a, bore 60 need only to be threaded andextend to intersect bore 56 a from one side face 52 and 54.

[0028] A semi-cylindrical indention 50 a is preferably located at theinner end of bore 56 a adjacent to cavity 50, although indention 50 amay be omitted if desired. The distal end of tube 38 is received in thebottom of indention 50 a when heat shield 24 is placed over heat sinkblock 22 a as shown in FIG. 8 to guide the distal end of tube 38 intoalignment with the inner end of bore 56 a. If desired, tube 38 a may beinclined at an acute angle α with the horizontal as shown in FIG. 2 tofacilitate alignment of the distal end of tube 38 with the inner end ofbore 56 a.

[0029] As shown in FIG. 8, after heat sink block 22 a has been welded tothe outer surface of furnace tube 23, a piece of common flexibleinsulation material 64 is placed over heat sink block 22 a and tube 38,and heat shield 24 is placed thereover. Heat shield 24 is connected tothe surface of furnace tube 23 by welding along the lower edges of sides52 and 54, and along the lower edges of ends 56 and 58 as shown in FIGS.9 and 10. Welding beads 66 shown in FIGS. 9 and 10 are welded along thelower edges of sides 52 and 54, and along the lower edges of ends 56 and58 of heat shield 24 to bond heat shield 24 securely to the outersurface of furnace tube 23.

[0030] Preferably, a generally cylindrical pin 62 preferably havingtapered distal end 62 a is utilized to lock thermocouple 42 inside heatshield 24. As shown in FIG. 10, thermocouple 42 is aligned to beinserted in bore 56 a and pin 62 is aligned to be inserted in bore 60.

[0031] After heat sink block 22 a and heat shield 24 are welded to tube23 with flexibly insulation material 64 therebetween, thermocouple 42 isinserted into bore 56 a and onward into tube 34 past vertical bore 40 ofheat sink block 22 a into the end 34 b of bore 34 a. Insulation material64 may be any conventional flexibly insulation material known in theart. The tapered distal end 62 a of pin 62 is then inserted into bore 60in the direction of the arrow adjacent to pin 62 in FIG. 60 and forcedtherein against shielded thermocouple 42 to lock thermocouple 42 tothermocouple holder assembly 20. As shown in FIG. 9, to removethermocouple 42 from thermocouple holder assembly 20, thermocouple pin62 is removed from heat shield 24 and thermocouple 42 is moved away fromheat sink block 22 a through heat sink tube 38 and through bore 56 a ofheat shield 24 in the direction of the arrow adjacent to thermocouple 42in FIG. 9.

[0032] The thermocouple holder assembly 20 of the invention eliminatesflame impingement under the heat shield 24, and isolates and insulatesthe heat sink block 22 a from the heat shield 24. The heat sink block 22a therefore only senses the temperature of the furnace tube 23 and isnot affected by radiant heat within the furnace.

[0033] Furthermore, a thermocouple held by the thermocouple holderassembly 20 of the invention is easily removable and replaceable withoutadditional welding. An old thermocouple may be removed and a newthermocouple may be installed during periodic, routine furnace shutdownusing the replacement pins and fasteners of the invention. No furtherwelding on tube 23 is necessary once the initial thermocouple holderassembly installation is complete.

[0034] Although the preferred embodiments of the invention have beendescribed in detail above, it should be understood that the invention isno sense limited thereby, and its scope is to be determined by that ofthe following claims:

What is claimed is:
 1. A thermocouple holder assembly for a furnace tubecomprising: a. a heat sink block for welding to said furnace tube, saidheat sink block having a first bore therein for slidably receiving thedistal end of an elongated sheathed thermocouple, said heat sink blockhaving a hollow heat sink tube extending from said first bore forreceiving a portion of said thermocouple, and b. a heat shield forwelding to said furnace tube having walls for shielding and completelyenclosing said heat sink block to shield said heat sink block fromambient heat on the exterior of said heat shield, said heat shieldhaving a cavity therein for receipt of said heat sink block and saidheat sink tube and flexible insulation material placed over said heatsink block and said heat sink tube, one of said walls having a secondbore extending therethrough to said cavity for slidably receiving saidthermocouple, said second bore being positioned in said heat shield wallfor alignment with said heat sink tube for conveying said thermocouplethrough said second bore to said heat sink tube, said heat shield havinga third bore extending through one of said walls and intersecting saidsecond bore for receipt of a fastener for placement in said third borefor selectively fastening said thermocouple to said heat shield and forselectively releasing said thermocouple from said heat shield.
 2. Thethermocouple holder assembly of claim 1 wherein said fastener is a pin.3. The thermocouple holder assembly of claim 2 wherein said pin has twoends and one of said ends is tapered.
 4. The thermocouple holderassembly of claim 1 wherein said heat sink block has a fourth boreintersecting said first bore and extending from said bore to the outsidesurface of said heat sink block.
 5. The thermocouple holder assembly ofclaim 1 wherein said heat sink block has a flat, generally rectangularbottom face for welding to said furnace tube.
 6. The thermocouple holderassembly of claim 5 wherein said bottom face has walls extending upwardtherefrom for welding to said furnace tube.
 7. The thermocouple holderassembly of claim 1 wherein said heat shield has a top rectangular faceand a partial rectangular bottom face parallel to said top facecontaining an opening to said cavity.
 8. The thermocouple holderassembly of claim 7 wherein said heat shield has four walls connected attheir edges and extending vertically between said top rectangular faceand said bottom face.
 9. The thermocouple holder assembly of claim 8wherein a semicircular indention is located adjacent to said cavity andthe interior end of said second bore to facilitate alignment of thedistal end of said heat sink tube with said second bore.
 10. Athermocouple holder assembly for a furnace tube comprising: a. anelongated sheathed thermocouple having a distal end for sensingtemperature, b. a heat sink block welded to said furnace tube, said heatsink block having a first bore therein slidably receiving said distalend of said elongated sheathed thermocouple, said heat sink block havinga hollow heat sink tube extending from said first bore slidablyreceiving a portion of said elongated sheathed thermocouple, and c. aheat shield welded to said furnace tube having walls for shielding andcompletely enclosing said heat sink block to shield said heat sink blockfrom ambient heat on the exterior of said heat shield, said heat shieldhaving a cavity therein receiving said heat sink block and said heatsink tube and flexible insulation material placed over said heat sinkblock and said heat sink tube, one of said walls having a second boreextending therethrough to said cavity slidably receiving saidthermocouple therein, said second bore being positioned in said heatshield wall in alignment with said heat sink tube for sliding saidthermocouple through said second bore to said heat sink tube, said heatshield having a third bore extending through one of said walls andintersecting said second bore having a fastener therein fastening saidthermocouple to said heat shield.
 11. The thermocouple holder assemblyof claim 10 wherein said fastener is a pin.
 12. The thermocouple holderassembly of claim 11 wherein said pin has two ends and one of said endsis tapered.
 13. The thermocouple holder assembly of claim 10 whereinsaid heat sink block has a fourth bore intersecting said first bore andextending from said bore to the outside surface of said heat sink block.14. The thermocouple holder assembly of claim 10 wherein said heat sinkblock has a flat, generally rectangular bottom face welded to saidfurnace tube.
 15. The thermocouple holder assembly of claim 14 whereinsaid bottom face has walls extending upward therefrom which are weldedto said furnace tube.
 16. The thermocouple holder assembly of claim 10wherein said heat shield has a top rectangular face and a partialrectangular bottom face parallel to said top face containing an openingto said cavity.
 17. The thermocouple holder assembly of claim 16 whereinsaid heat shield has four walls connected at their edges and extendingvertically between said top rectangular face and said bottom face. 18.The thermocouple holder assembly of claim 17 wherein a semicircularindention is located adjacent to said cavity and the interior end ofsaid second bore to facilitate alignment of the distal end of said heatsink tube with said second bore.